1. Technical Field
The present invention relates to a chucking device operable to allow a disc, which is for storing and reproducing data, to be attached thereto and removed therefrom, and relates to a motor and to a disc drive device having loaded thereon the chucking device.
2. Description of the Related Art
Conventionally, a chucking device has been developed as means to allow a disc, which is for storing and reproducing data, to be attached thereto and removed therefrom, and to adjust (hereinafter referred to as align) a center of rotation of the disc to a rotation center of a motor. Further, there are expectations in which such chucking device becomes compatible with a high-density multilayer disc such as one illustrated in FIG. 11.
The multilayer disc 1 illustrated in FIG. 11 comprises two discs, 1a and 1b, pasted to one another using an adhesive. The discs 1a and 1b each are provided therein, for example, a 15 mm central opening space.
According to a technical standard: a maximum allowable internal diameter of the central opening space (e.g., 1a1 and 1b1, respectively) for each discs 1a and 1b are between 15.00 mm to 15.15 mm while a minimum allowable internal diameter of the 1a1 and 1b1 for the discs 1a and 1b after they are pasted to one another is 15.00 mm; and a maximum allowable misalignment between two discs after they are pasted to one another is, as illustrated in FIG. 12, 15.15 mm at the central opening space wherein the discs are misaligned from one another in opposite directions by, in total, 0.15 mm.
When the chucking device aligns the multilayer disc 1 comprised of 1a and 1b that are misaligned from one another by, in total, 0.15 mm at their central opening spaces with the chucking device, it is difficult for the chucking device to accurately align the multilayer disc 1 with the chucking device.
To this end, a chucking device (e.g., chucking device 2) as illustrated in FIG. 13 has been proposed. A structure of the chucking device 2, illustrated in FIG. 13, comprises a stator unit section 2a and a movable section 2b. The movable section 2b includes: a retainer section 2b1 for making contact with the disc 1b, which is a bottom half of the multilayer disc 1, so as to retain the multilayer disc 1; an inclined guiding section 2b2, which is adjacent to the retainer section 2b1; a contact prevention inclined section 2b3 for preventing the disc 1, which is a top half of the multilayer disc 1, from making contact with the chucking device; and a supporter section 2b4 for supporting the retainer section 2b1, the inclined guiding section 2b2 and the contact prevention inclined section 2b3.
Due to the chucking device 2 in which the movable section 2b makes contact solely with the disc 1b of the multilayer disc 1, an alignment between the multilayer disc 1 and the chucking device is to be executed based on the disc 1b. 
However, due to the contact prevention inclined section 2b3, an angle generated by the inclined guiding section 2b2 and a rotation axis J1 will be forced to be large. Therefore, when the disc 1b makes contact with a radially inner side of the inclined guiding section 2b2, the movable section 2b will be forced to elastically bend its shape considerably outward in a radial manner so as to guide the multilayer disc 1 to the retainer section 2b1. Consequently, when loading the multilayer disc 1, a large force (e.g., a disc loading force) needs to be applied axially downward. As such, when the large disc loading force is required for loading a disc, there may be situations in which the disc is no fittingly loaded (e.g., clamp error) before a contact is made between the disc and the retainer section 2b1.